Priestley and Doherty played twins Brandon and Brenda Walsh in the hit 1990s show about teenagers living in the exclusive neighbourhood of Los Angeles.

Doherty, 45, revealed in August last year that she had been diagnosed with breast cancer five months previously.

She has been documenting her battle with the disease on social media, and recently shared a set of images of herself shaving her head and going through chemotherapy.

Last month she settled a lawsuit against her former business managers, who she said left her without health insurance and caused a delay in receiving her diagnosis.

Priestley told the Press Association: " We are all very worried about Shannen and feel for her but we all know her and how tough she is and she has never shied away from a fight.

"We are very hopeful she will beat cancer like she has beaten everything else. She's a tough kid."

Priestley, who is soon set to play a private investigator in new series Private Eyes, revealed he is still inundated with fan questions about his years on Beverly Hills, 90210, despite the show ending its 10-year run in 2000.

He said: "People always want to know about 90210 because that show was iconic for a lot of people. It was on for so long and it was a big part of people's lives, an important part of their lives."

Although Priestley, 47, is still associated with a role he played in his 20s, he does not begrudge it. He said: "I have always found it to be beneficial for me. It opens doors for me and it always has."

Priestley rocketed to fame when he was cast in the show, and even appeared on the cover of Rolling Stone magazine with Doherty and their co-star Luke Perry. But he thinks it was easier to be a young celebrity in the 1990s than it is today.

He said: "I think being famous now is more difficult than it was back then. Everyone has a phone and everyone is documenting everything.

"It depends on the person though. I was very conscientious about the work I was doing, I put myself in situations where I was working all the time. I didn't have the opportunities to get into too much trouble. Idle hands are the devil's plaything."

Priestley's new show is set in his native Canada, where it has already enjoyed great success.

He said the chance to play an investigator allowed him the chance to revisit programmes he loved as a child.

He added: "I grew up on a steady diet of shows like Magnum P.I. That was my generation and we grew up with those characters - that was who we idolised. To get to play a guy like that is a dream."

:: Private Eyes starts on Monday September 19 at 8pm on Universal Channel.